EDINBURGH — Alex Salmond, who led Scotland’s failed bid for independence, announced on Friday that he would step down as first minister of Scotland and leader of the Scottish National Party later this year.

The unexpected announcement came the day after voters spurned the vision of Scottish sovereignty that had propelled his political career for decades, and voted decisively in a referendum to continue Scotland’s 307-year-old union with Britain. Mr. Salmond was by far the most prominent casualty of the defeat.

The independence campaign that he led sent shock waves through Britain’s political elite, energized Scottish politics as rarely before and appeared to open the way for a looser, more federal Britain. After starting far behind in the polls, the independence campaign appeared to close the gap in the increasingly suspenseful final weeks, and in some surveys it even seemed to take a slight lead.

But when the ballots from all 32 voting districts were tallied early Friday, the “no” campaign had won 55.3 percent of the vote.

Referring to the seats of the British and Scottish Parliaments, Mr. Salmond said in a statement, “Today the point is this: The real guardians of progress are not the politicians at Westminster, or even at Holyrood, but the energized activism of tens of thousands of people who I predict will refuse meekly to go back into the political shadows.”

“For me right now, therefore, there is a decision as to who is best placed to lead this process forward politically,” he continued. “I believe that in this new exciting situation, redolent with possibility, party, Parliament and country would benefit from new leadership.”

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Alex Salmond in Edinburgh on Friday.CreditMatt Cardy/Getty Images

Therefore, Mr. Salmond said, he will not stand for re-election as leader at his party’s annual conference in November, and then will resign as first minister “to allow the new leader to be elected by due parliamentary process.”

“We lost the referendum vote, but can still carry the political initiative,” he said. “More importantly, Scotland can still emerge as the real winner.”

His decision to resign reflected the deep disappointment on Friday within the vocal, enthusiastic pro-independence movement, which saw the referendum as a rare opportunity to make a centuries-old nationalist dream a reality.

At a news conference in Edinburgh, Mr. Salmond, who was ebullient, feisty and sometimes pugnacious during the campaign, seemed to turn wistful. “For me as leader, my time is nearly over,” he told reporters, “but for Scotland the campaign continues, and the dream shall never die.”

Mr. Salmond did not identify a successor, but political analysts said his deputy, Nicola Sturgeon, who played a central role in the campaign, was likely to be a strong contender.

British political leaders promised on Friday to heal the wounds opened by the referendum and begin work on sweeping changes to give new decision-making powers to Scotland and other parts of the country — changes that the three main British political parties promised in the panicky last days before the referendum, though they have yet to agree on specifics.

Negotiations on those changes are likely to be tortuous, and not just between London and the Scots.

“The old union we know is dead,” said Carwyn Jones, the first minister of Wales. “We need to forge a new one. But no more committees, no more messing about, no more panicky deals — it’s time to sit together, all of us as four nations, and work this through.” Northern Ireland is the fourth component of the United Kingdom, along with England, Scotland and Wales.

Among the outstanding issues is whether England should continue to be ruled solely by the national Parliament in Westminster, which includes Scottish, Irish and Welsh members, or be given some form of regional government as well, akin to those in Scotland, Ireland and Wales.

In Edinburgh, Mr. Salmond said earlier in the day that the 1.6 million votes cast for separation showed the depth of the desire for greater decision-making powers in Scotland. “Today of all days, as we bring Scotland together, let us not dwell on the distance we have fallen short, let us dwell on the distance we have traveled,” he said.

For Prime Minister David Cameron, whose job would have been on the line had the Scots voted to break away, the referendum results were an evident relief, though one tempered with an awareness that it may have won by his late promise of new powers for Scotland, which already controls health and education within its borders.

Mr. Cameron said Friday morning that there could be “no disputes, no reruns,” and that the referendum had settled the independence debate “for a generation.”

Queen Elizabeth II, who is precluded from intervening in politics, urged Scots on Friday to seek unity and work together in the wake of the vote. “For many in Scotland and elsewhere today, there will be strong feelings and contrasting emotions – among family, friends and neighbors,” she said in a statement from her Scottish castle at Balmoral. “Now, as we move forward, we should remember that, despite the range of views that have been expressed, we have in common an enduring love of Scotland, which is one of the things that helps to unite us all.”

With its appeal for a fresh start, the “yes” campaign seemed to capture the imagination of a large section of Scottish electorate that was bitterly disillusioned with London politics. By contrast, the “no” side stressed the economic risks of a breakaway, and was accused of running a negative campaign.

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Leaders from Britain, Scotland, Spain and the European Commission spoke after Scotland rejected independence from Britain in a referendum.CreditCreditAndrew Milligan/Press Association, via Associated Press

On Friday the result was welcomed by the Confederation of British Industry, a leading business lobby group. “This is a momentous day for our United Kingdom, and this result will be greeted by a collective sigh of relief across the business community,” said John Cridland, the organization’s director general.

The outcome was no less welcome in Washington, where President Obama had made little secret of his desire that Britain remain intact, not least because of Mr. Salmond’s promise to evict British nuclear submarine bases from an independent Scotland.

“We have no closer ally than the United Kingdom, and we look forward to continuing our strong and special relationship with all the people of Great Britain and Northern Ireland as we address the challenges facing the world today,” Mr. Obama said in a statement.

The NATO alliance and the European Commission, the executive body of the 28-nation European Union, also welcomed the rejection of a referendum that had already encouraged separatists in other parts of Europe, including the Catalonia region of Spain.

In Madrid, Prime Minister Mariano Rajoy called the Scottish vote “the most favorable option for everyone — for themselves, for all of Britain and for the rest of Europe.”

But Artur Mas, the head of Catalonia’s regional government, drew a different interpretation, saying that Scotland had provided “a great lesson in democracy” and urging Mr. Rajoy to follow Mr. Cameron’s example and permit a similar referendum there.

“To think you can shut up a Catalan society that wants to vote isn’t going to work in a democracy of the 21st century,” Mr. Mas said in Barcelona.

A version of this article appears in print on , Section A, Page 1 of the New York edition with the headline: Scottish Leader, Alex Salmond, to Resign After Losing Vote on Independence. Order Reprints | Today’s Paper | Subscribe